Because of the effects indoor air has on health, comfort and durability, indoor air quality in our homes is becoming of increasing concern to many people. The Environmental Protection Agency lists poor indoor air quality as the fourth largest environmental threat in our country. Asthma is leading serious chronic illness of children in the U.S. and moisture-related construction defects and damage are on the increase in new houses. Minimum residential ventilation can improve many of these indoor air quality problems.
The most current standard describing residential ventilation practice for acceptable indoor air quality is Standard 62.2-2004, published by the Association of Heating, Refrigeration, and Air-conditioning Engineers in Atlanta, Ga. As a standard for use in regulation, 62.2 describes the minimum requirements for mechanical and natural ventilation systems that are necessary to provide minimally acceptable indoor air quality for typical situations. Standard 62.2 is applicable to both new and existing homes, including all single-family homes and small multi-family ones.
Local ventilation, such as vented range hoods and bathroom and laundry exhaust fans, is intended to exhaust pollutants from specific rooms in which sources are expected to be produced before they enter the general environment. Whole house ventilation, such as integrated with central air conditioning systems, is intended to bring fresh air into the general environment to dilute pollutants that cannot be effectively controlled at the source.
In central air conditioning systems, the conditioned air is distributed by the air distribution fan or blower, through various ducts throughout an indoor space in order to place the conditioned air at desirable locations. Generally, a thermostat and/or humidistat are used to activate the central air conditioning system. For example, when the indoor air temperature drops below a selected level, the air temperature sensor and switch in the thermostat can activate the heating apparatus and the air distribution fan. Likewise for indoor air temperatures above a selected level, and air humidity above or below corresponding selected levels, the thermostat and/or humidistat activate a cooling apparatus, dehumidifier or humidifier, respectively, and the air distribution fan.
Unlike central air conditioning systems, indoor local ventilation systems are usually manually operated by the user. Residential ventilation systems can be exhaust, supply, or balanced in terms of the air pressure effect on the interior of the building with respect to the outdoors. These systems can be multi-point or single-point, meaning that the air can be exhausted from or supplied to many points or a single point. Single point ventilation systems, typically exhaust fans, are not integrated with the operation of the central air conditioning system and have poor distribution of ventilation air. When activated, the exhaust fan exhausts indoor air for the time period that the exhaust fan is activated. However, the exhaust fan may not be activated as often as required and when activated, the time period for the activation may not be adequate. For example, the range hood fan is not usually activated when the kitchen is used to prepare food unless the preparation generates offensive odors or strong pollutants such as smoke, prompting the user to activate the overhead fan. When preparing food without activation of the overhead fan, the pollutants produced are not exhausted and therefore they enter the general environment.
A known prior art control systems for periodically operating the air distribution fan of the central air distribution system are disclosed in U.S. Pat. Nos. 5,547,017, 5,881,806 and 6,431,268 issued to Armin Rudd on Aug. 20, 1996, Mar. 16, 1999 and Aug. 13, 2002, respectively, the same inventor as the present invention and which are hereby incorporated by reference thereto. The air distribution cycling control systems periodically operate the air distribution fan for a first selectable time period after a second selectable time period from the end of the last operation of the air distribution fan. Simply put, it operates the air distribution fan dependent on prior operation of the fan. However, no known control systems exist for controlling the periodic operation of both a household ventilation fan and the air distribution fan, depending on prior operation, for ventilation and air mixing.
Prior art related to the air distribution and ventilation cycling portion of the present invention are cited but were not found to overcome the problems cited above. See for example, U.S. Pat. No. 4,898,086 to Norris wherein a photoelectric device in conjunction with a relay actuates a fan to ventilate the house for a period of time determined by a time delay device. The photoelectric device detects a change in outdoor lighting, such as sunrise, to activate the fan.
U.S. Pat. No. 5,772,887 to Wolfson et al. describes an automatic program ventilation control system that allows a user to programmably select a duty cycle, a time of day and a fan speed to automatically operate a fan for a specified length of time within a specific time interval. The programmable system also includes a manual override for manually activating the fan at a selected speed for a selected time. However, the system fails to provide alternative selectable modes of operation of the fan such as continuous operation and manual operation only, and fails to base the interval on prior operation of the ventilation fan due to automatic cycle operation and manual activation. The Wolfson et al. system also fails to provide optional modes for activation of the fan in conjunction with operation of a blower of a central air conditioning system.
U.S. Pat. No. 5,971,067 issued to Rayburn, et al., provides an air quality system that requires a sensor for sensing the quality of the indoor air and drawing in additional outdoor air when a problem is detected
U.S. Pat. Appl. Pub. No. 20030127914 to Homan, Timothy C. et al., discloses a system that activates the exhaust fan when the light is switched on and causes the fan to continue operation for a time period after the light is switched off.
U.S. Pat. No. 6,318,639 issued to Toth describes a thermostat with temporary fan on function for selecting a predetermined time for enabling operation of the air circulating fan and a period of time for the operation.
Also see U.S. Pat. No. 6,695,218 issued to Fleckensein which provides a system that monitors air conditioning operation and performs calculations to determine when the building circulation fan would improve the comfort level.
The prior art fails to automatically activate an existing ventilation fan based on prior operation of the ventilation system and/or in conjunction with the operation of the central air distribution system. The present invention provides a means for a user to select a ventilation fan operational mode and optionally includes operation in conjunction with the operation of the air distribution fan.
In a first embodiment, the system is selectably set for continuous operation, manual operation, or operation of the ventilation fan for the minimal time selected per cycle interval, including operation due to manual user demand. In a second embodiment, the controller provides an effective, automatic means to effect exhaust, supply, or balanced ventilation, or a combination thereof, in conjunction with operation of the central air conditioning system for improved distribution of ventilation air. In a third embodiment, the cycling system includes a means for making sure that the central air distribution fan is ON, for a minimum selected or determined time per interval, including operation due to demand from, at least one of, a thermostat, humidistat, and dehumidistat Optionally, the outside air damper would be cycled off (closed) independent of the air distribution fan if the minimum selected or determined ventilation time was accomplished.